As is known, in the automotive industry, electric connecting units are used comprising two complementary connectors mating in a predetermined direction.
Each connector normally comprises an insulating casing defining a number of cavities for housing respective electric terminals and having respective axes parallel to the mating direction of the connector to the complementary connector.
The terminals are retained inside the respective cavities by flexible primary retaining lances normally formed in one piece with the casing.
More specifically, the lances project inside the respective cavities from one of the walls defining the cavities, and are deformable elastically in a direction crosswise to the mating direction of the connectors to click inside respective seats for receiving the terminals.
Alternatively, in another known solution, the flexible lances are formed in one piece with the terminals, and click inside respective retaining seats formed in the walls defining the respective cavities.
Known connectors also comprise a secondary retaining device for determining correct insertion of the terminals inside the respective cavities, and which also acts as a further safety device for ensuring retention of the terminals inside the cavities.
The secondary retaining device normally comprises a movable member which clicks onto the casing, and which may either be hinged integrally to the casing or defined by a separate member. In both cases, the movable member can only click onto the casing when the terminals are all fully inserted correctly and retained inside the respective cavities by the primary retaining lances.
Two widely differing types of secondary retaining devices exist, depending on the direction in which the movable member engages the casing.
In a first type, the movable member engages the front of the casing, i.e. in a direction parallel to the mating direction of the connectors. Examples of this type of secondary retaining device are described and illustrated in Patent Applications EP-A-1107383 and EP-A-1257007.
As described in the above applications, the movable member is defined integrally by a plate and a number of wedges projecting perpendicularly from the plate. Each wedge is inserted between the respective primary retaining lance and the wall from which the lance extends; and, in the event one of the terminals is not correctly or fully inserted inside the respective cavity, the respective primary retaining lance remains deformed, thus preventing insertion of the respective wedge. Once the movable member correctly engages the casing, the wedges prevent the primary retaining lances from deforming accidentally and so releasing the terminals.
In other words, the movable member cooperates directly with the primary retaining lances to prevent undesired deformation of the lances in use, but in no way interacts with the terminals, which are therefore retained solely by the primary retaining lances.
In the second type of secondary retaining device, the movable member is inserted laterally inside the casing, i.e. crosswise to the mating direction of the connectors.
In this case, the movable member is positioned with portions of it facing respective shoulders on the terminals, so as to define terminal stops in the withdrawal direction and so actually perform a secondary retaining function, i.e. in addition to that of the primary retaining lances.
In situations requiring airtight connecting units, i.e. with sealing means interposed between the mating portions of the two connectors defining the unit, laterally inserted secondary retaining devices cannot always be used.
That is, to avoid impairing the seal, laterally inserted secondary retaining devices can only be used on the portion of the connector designed to fit inside the other connector, whereas, on the outer connector, front-engaging secondary retaining devices must be employed, but which, as stated, do not actually perform any secondary retaining action on the terminals.